Re: Oracle file managerCLOSE

In article <1992Sep25.214444.8180_at_tamsun.tamu.edu>, pnarayan_at_cs.tamu.edu (P S Narayan) writes:
> Hello,
> This one is on Oracle File Manager.
> This is relevant to version 6.0.
> Suppose that I have a partition /dev/sd3g. I have a directory /oracle on which
> is /dev/sd3g mounted. If I use the Create database statement to create one
> data file "mydb" and two redo log files "redo1" and "redo2", from the
> Unix shell prompt when I do "ls", I can see the three files
> "mydb", "redo1" and "redo2" under oracle directory.
> Does this mean that Oracle Filemanager is interacting with the UNIX file
> manager and actual inodes are being created for these files ?
> If inodes are being created, then does oracle access these files using
> inode pointers or is it merely for listing the files for user's convenience ?
> I don't see any reason why oracle should traverse the files using filesystem
> inode pointers. Most files may be contiguously allocated and Oracle should
> internally keep a directory of all files for a table to read the table.
> Am I right or wrong. Please correct me.
> I am sorry if I have confused you.
>
> Thanks for any reply
> Narayan
> pnarayan_at_cs.tamu.edu

Oracle -- a file manager!!! How dare you! At least a few people still believe
it is a relational database.

The database is stored in a set of UNIX files. When you issue "create
database", it does a "creat" system call to create unix files in the
$ORACLE_HOME/dbs directory. If ORACLE created it's own file structure, you
wouldn't be able to back them up using normal UNIX commands. So, yes, inodes
and dnodes are created for these files, they are stored and accessed the same
as any other filesystem. If Oracle kept a directory of contiguosly allocated
disk pointers, you would never be able to recover from disk crashes or restore
from backups. The drawbacks of using unix files for data storage are
relatively small since both Oracle and UNIX depend on memory caching frequently
accessed data. I don't know if the files are contiguous anymore. In Oracle V5
you used to have to manually create your data files with a utility called
"ccf", (create contiguous file). I know that those datafile contain some
internal indexes into the rest of the file but I don't know what the structure
of these indexes are.